Below is a proof showing that the sum of a rational number and an irrational number is an irrational number.

It is the sum of two rational numbers

Step-by-step explanation:

Given that a is a rational number and b is an irrational number.

To prove that a+b is irrational.

Here contrapositive method is used to prove

If possible assume a+b is rational and equal to x

Then we have

a+b = x

b = x-a = x+(-a)

On right side we have sum of two rational numbers hence right side is rational.

But left side b is irrational thus a contradiction

to determine the unit cost your would divide the total cost by the number sold.

7 bagels for $4.41       $4.41/7 = $.63 each at fresh side

5 bagels for $3.60         $3.60/5 = $.72 each at value mart